The dispensing of flowable materials in a contamination-safe manner, especially over prolonged periods of time or in a repetitive manner, e.g., in multiple doses, presents many difficulties. The main problems relate to precise flow control and prevention of back flow or reflux. In a conventional dispensing system, external contaminants easily can enter the container with the back flow at the end of the delivery cycle.
Most collapsible containers for flowable materials have a discharge port such as a hole, nozzle, spout or other type of opening. The contents of the container, such as pastes, liquids or other fluids, exit through the discharge port propelled by internal pressure. This method of dispensing the flowable material is frequently inaccurate and does not prevent the entry of external contaminants into the container. Hence, additional pouring or dispensing devices must be mounted on or in the discharge port when precise control of the dispensing characteristics is desired. These devices must be simple, effective and low-cost, especially if intended for widespread commercial and domestic use.
A number of patents have been issued on flow control valves and devices for heavy industries. For example, Colvard, U.S. Pat. No. 5,411,049 discloses a flow control valve for cementing equipment used in well-boring operations. The valve allows fluid flow in either direction. Swearingen, U.S. Pat. No. 5,392,862 teaches a flow control sub for hydraulic tools used in mud flow drilling operations in oil fields. Mueller et al., U.S. Pat. No. 5,181,571 teach a device and process for well drilling and setting liners for oil, gas and other completions. U.S. Pat. Nos. 4,067,358 and 3,957,114 issued to Streich describe additional valves for cementing operations.
All of the foregoing flow control valves are adapted for heavy machinery in field conditions and can not be adapted to maintain sterility of systems in which they are used. Specifically, such flow control valves are not adapted to ensure one-directional flow (some of the devices, in fact, permit free reflux) and can not be fitted on collapsible containers. Furthermore, these devices contain many parts and are typically expensive, each costing hundreds or thousands of US dollars.
Typically, a dispensing apparatus has a valve mechanism to ensure precise delivery. U.S. Pat. No. 5,033,655 teaches how to dispense fluid products from a non-collapsible container by employing a system with a slit valve. The system admits air to prevent the collapse of the container as fluid is delivered to the user. This has a disadvantage in that external contaminants borne by air are forced into the solution remaining in the container. Clearly, such a dispensing apparatus is not suitable for contamination-safe multi-dose dispensing from a collapsible container.
A simple solution in the form of a squeeze valve with augmented sealing is presented by U.S. Pat. No. 5,265,847. This apparatus is adapted for a container whose contents are expelled under the force of gravity. U.S. Pat. No. 5,099,885 discloses a flapper valve, which delivers viscous fluids by means of a pump. This solution is not applicable to all types of liquids and fluids. For example, a flapper valve is not appropriate for highly viscous material and is not useable for suspensions or dispersions.
Likewise, in U.S. Pat. No. 5,346,108 Pasinski discloses a gauged dispensing apparatus to deliver a predetermined amount of generally viscous fluid. The apparatus has a flexure with a bi-stable orientation, concave to convex. Airborne contaminants can enter the apparatus as the flexure returns to its original position. In the devices of Vorhis, Nilsson and Pasinski air and its contaminants rush in to replace the volume of the solution discharged. These devices are not claimed to be contamination-safe.
In addition to the shortcomings already mentioned, the above prior art solutions are not specifically designed to prevent back flow. Haviv teaches in his U.S. Pat. No. 5,080,138 a valve assembly relying on a sleeve valve and consisting of multiple components. Back flow is thwarted by a sheath which permits the flowable to flow out of the valve but prevents any back flow into the container. Unfortunately, this device is complicated, costly to manufacture and difficult to assemble.
A simple discharge nozzle is presented by Latham in U.S. Pat. No. 5,398,853. The nozzle is adapted for the delivery of pastes, e.g., toothpaste. Although Latham does attempt to eliminate the transfer of germs between the discharge opening and the secondary surface where the paste is applied, his nozzle will not arrest the influx of bacteria. For example, bacteria can enter when the nozzle is immersed in a solution.
More effective methods of contamination-free dispensing are disclosed in U.S. Pat. Nos. 5,305,786 and 5,092,855 issued to Debush and Pardes respectively. Debush discloses a modification to the applicant's prior U.S. Reissue Pat. No. 34,243 relying on an expandable elastomeric sleeve tightly fitted about a valve body with entry and exit ports. Debush's improvement is aimed at simplifying the assembly. Unfortunately, his solution requires more material and considerably increases the cost of manufacturing the valve. In addition, it is difficult to produce a discoid-shaped valve while at the same time adapting the apparatus to collapsible containers. Pardes discloses a rigid enclosing sleeve to retain the elastomeric sheath against the valve body, thus providing a seal between the sheath and the valve body. This is closely related to the applicant's teaching in U.S. Reissue Pat. No. 34,243. Pardes' valve operates through two sets of ports within a valve body, thus rendering the device and its manufacture unnecessarily complex.
The foregoing solutions have disadvantages in that they cannot be downsized for small containers. The ratio of length to diameter is large and thus limits the volume of flow for small containers.
None of the prior art dispensing devices are low-cost, simple in construction and capable of delivering a flowable material ranging from low to high viscosity in multiple doses in a contamination-safe manner.
In view of the foregoing, it is apparent that what is needed is a system which provides a multi-dose dispensing system for flowable materials in which the sterility or purity of the flowable material is preserved. In particular, the system of the present invention prevents contaminants from passing backwards through the valve into the reservoir of flowable material.
What is also needed is a simplified system for dispensing a flowable material without airborne contamination which is adaptable, simple in construction and mountable on or in any container of the type which maintains its own internal pressure, i.e., not produce a substantial internal vacuum when the flowable material is dispensed. Examples of such containers are volumetrically reducible containers such as a flexible tube, flexible bag or a flexible bottle. The container also could be a vented rigid container including a flexible bag of flowable material.
What is also needed is an improved system for preventing air or airborne contaminants from entering a flowable material comprising a powder such as talc, or the like. The system should also be applicable to a medicine delivered as a powder or aerosol where it is important to prevent airborne contamination from fibers, dust, pollen, microorganisms, or like forms of airborne contaminants.
Other objects and advantages of the invention will become apparent upon reading the detailed description of the invention.